In digital broadcasting, MPEG (Moving Picture Experts Group) 2 method is adopted as a video data encoding method. In MPEG-2 encoding, video data is divided into three kinds of data including an I-picture, a P-picture and a B-picture, and these data are grouped in units of a GOP (Group Of Picture).
The I-picture is formed by compressing one frame of image itself just as it is, and it has a low compression ratio and a high degree of accuracy. The P-picture is formed by prediction (forward direction prediction) from a previous I-picture and/or a previous P-picture, and it has a higher compression ratio than that of the I-picture and a similar degree of accuracy to that of the I-picture. The B-picture is formed by prediction (bidirectional prediction) from a previous or future I-picture and/or a previous or future P-picture, and it has a higher compression ratio than that of the P-picture and a similar degree of accuracy to that of the P-picture.
In this MPEG-2 method, since the I-picture has all information by itself, it is possible to be decoded from itself. However, since the P-picture and the B-picture have only difference information, it is impossible to decode them without using a prediction image.
In other words, when a channel is switched in a conventional digital broadcast receiving apparatus, decoding of the video data begins after an I-picture included in video data of the switched channel appears. Since an I-picture is located at a beginning portion in a GOP and the GOP is formed from 15 frames, it is necessary to wait approximately 0.5seconds at the maximum for appearance of an I-picture and this interval is an image non-displaying period, during which no image is displayed.
As a technique of shortening such image non-displaying period, for example, Patent Document 1 describes a technique of switching a display in synchronization with appearance timing of an I-picture of video data after channel switching.
For example, in Patent Document 1, when the channel switching is operated, the image non-displaying period is shortened by displaying an image of a channel before channel switching until a switching time satisfying the following equation (1).(appearance time of I-picture)+(interval between I-pictures)−(period-of-time for tuner setting)−(current time)< 1/30 seconds  (1)
In this connection, the appearance time of I-picture is a time when a preceding I-picture was obtained, the interval between I-pictures is a time interval between times at which the I-picture is obtained, and the period-of-time for tuner setting is a period of time required for setting a tuner.